Tetrahydropyran-sulfide compounds



Patented July 24, 1951 TETRAHYDRorY r-smsoLrme-comroui ns Frank Kipnis, Cleveland, Ghio, assignor to Amer loan Home .Foods lnc New lork N. 1., mor

porationof New Jersey;- 3

No Drawing. Application-September'19, 1949,

SeriaijNo. 116 63;"; r

1 This invention relates to 'tetr'ahydropyranesul fide compounds. More particularly it relates to '2"-substituted tetrahydropyranyl sulfides and their preparation by catalytic addition of one molecule of 'a'l'ower alkyl or aralkyl mercaptan to one molecule of dihydropyran. By lower alkyl or aralkyl I mean groups containing not 7 more than 8 carbon atoms.

The new compounds areli'quids with pleasant minty aromas; they are quite stable to alkali, but are decomposed. by dilute acids. They have potential value as constituents of flavoring and odor-masking compositions, and as chemical intermediates. I

Relatedoxygenethers have been prepared, but as far as I know they have little or no practical importance. compounds appears at least in part dependent cn-th'e presence of the bridge sulfur in the. molecule.

I have. discoveredthat these compounds can bamade by reacting equimolar amounts of'dihydropyran and a lower alkyl or aralkyl mercaptan in the presence of a small percentage of anhydrous hydrogen halide such as HCl, the reaction being initiated at ice-bath temperature (0-10 C.) and completed at steam-bath temperature (up to 90 C.). No solvent medium is required for the reaction beyond a small amount of medium such as anhydrous ether, a convenient vehicle for the hydrogen halide. After completion of the reaction, the catalyst is neutralized, as by washing with an alkali carbonate solution, dried, stripped of volatiles and fractionated, e. g. under low pressure, preferably less than 10 mm. of Hg. The reaction may be represented by the following equation in which R is an unsubstituted alkyl (including aralkyl) group containing not over 8 carbon atoms:

Thedesirable minty aroma of my Her)" S-R One embodiment of my invention is shown in the following example, itnen'ded to be illustrative only and not to limit the scope of my invention, whichis defined in the appended claims.

Ethyl 2-te tra7zydropyranylv sulfide.-To a v 300 ml. pressurebottle chilled in an vice 'bathwas added 15.5.g. (0v.25 mole), of ethyl mercaptan, 21 g. (0.25 mole) of dihydropyran and 5 mg. of hydrogen chloride in 1 ml. of anhydrous ether. Thgbottlewas ,stopp'ered immediately, shaken. thoroughly and'thecontents allowedto Warm toroomtemperature, after which the temperature: wasmaintained'at 90f for 3 hours. At the-end ofjthis', timahthe bottle was chilled andopened,

thehcontentswashed into a separatory funnel with ml. of ether and then shaken with 5 ml. of saturated potassium carbonate solution and v separated. The organic layer was dried over calcium sulfate, filtered,

residue was fractionated through a 20 cm.. Vigreux column to give a 40.5% yield of a colorless oil boiling at 4 under 2 mm. Hg pressure.

Treatment with ammoniacal sodium nitroprusside gave no coloration, indicating absence of unreacted mercaptan as well as stability of the sulfide to alkali. Treatment of the sulfide with sodium nitrite-hydrochloric acid caused the development of a red color indicative of easy hydolysis to the initial ethyl mercaptan, while an immediate pink color was given with the fuchsinsulfur-dioxide reagent, confirming hydrolysis to the open chain hydroxyaldehyde.

and the volatiles:- stripped under slightly reduced pressure. The- 4 amount of an anhydrous hydrogen halide catalyst at approximately -10 C. in the presence of a small amount of volatile organic solvent, warming the mixture under its own equilibrium The compounds listed in the following table have been made in a similar way with the yields indicated; boiling points, empirical formulas and analyses are also shown.

TABLE I Tetrahydropvranyl sulfides Analysis R B. P. "0 filf 3 1111 1 Calculated Fsund o H s o H, s

57.8 54.50 9.14 54.72 9.21 10.5 51.49 9.05 21.92 07.51 9.99 21.07 20.7 59.95 10.00 20.00 00.09 9.70 20.74 00.7 59.05 10.00 20.00 59.10 10. 23 20.30 n-Hexy 84-6 (2.5mm. 25.0 05.29 10.90 15.84 05.31 10.49 15.23 Benzyl 90-1 2 mm.) 42.9 ounwosmu 09.19 7.14 15.39 09.59 9.00 15.43

I claim: pressure to a steam-bath temperature and main- 1. Z-substituted tetrahydropyranyl sulfides taining it at such temperature for a sufiicient having the formula: 25 time to complete the reaction, neutralizing the reaction mixture, removing volatile solvent therefrom, rectifying the mixture by fractionally distilling' it under vacuum, and separately recovs R ering a Z-substituted tetrahydropyranyl sulfide 0 fraction.

in which R is selected from the class consist- The M09855 defined in m? in which w mg of alkyl groups and aromatimhwrocarbom H hydrogen halide is 1101, the vehicle therefor is substituted alkyl groups containing not over 8 ethyl ether, the neutralization is effected by carbon atoms Washing with an aqueous alkali carbonate solu- 2. Methyl 2tetrahydropyran lfide, tion, and the neutralized mixture is dried over a Ethyl 2 tetrahydropyran u1fid solid dehydrating agent prior to removal of the 4. Propyl 2-tetrahydropyran sulfide. Solvent and rectification- 5. I-Iexyl 2-tetrahydropyran sulfide. FRANK KTPNIS- 6. Benzyl Z-tetrahydropyran sulfide.

7. The method of synthesizing 2-substituted 40 7 REFERENCES CITED tetrahydropyranyl sulfides which comprises mix- The fonowing references 6 of record in the ing in a pressure vessel equimolecular amounts file of 171115 Patent: of dihydropyran and a mercaptan selected from Kai-re, Organic Chemistry, ed. 2, page 114, the class of alkyl and aralkyl mercaptans con- E1 vi r, 1946, Chem Eng News, 25 2931 taining not over' 8 carbon atoms with a small Certificate of Correction Patent No. 2,562,042 July 24, 1951 FRANK KIPN IS It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 7, for itnended read intended; lines 36 and 37, for hydolysis read hydrolysis; columns 3 and 4, in the heading to the last three columns, for Faund read Found; same table, under the heading Found, second line, under C, for 67.57 read 57. 57; same table, under the heading Found, third line, under S, for 20.74 read 20.75; same table, under the heading Found, fifth line, under S, for 15.23 read 15.52; column 4, line 43, under REFERENCES CITED, for Karre read Kari-er;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 6th day of November, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. 2-SUBSTITUTED TETRAHYDROPYRANYL SULFIDES HAVING THE FORMULA: 